高空急流以及低空低涡作用下的一次降水研究

A Study of Precipitation under the Interaction between Upper Level Jet Stream and Low Level Vortex

摘要: 文章采用中国自动站与CMORPH降水产品融合的逐时降水量网格数据资料及NCEP-FNL再分析资料，运用天气动力学诊断方法对2016年7月18~21日发生在豫北与河北南部一带的暴雨主要天气形势和动力成因进行了分析。结果表明，暴雨发生在“东高西低”的有利环流形势下。200 hPa高空急流发展增强，高空急流入口区右侧出现较强辐散。低空700 hPa有西南低涡发展并加强东移，造成其东北侧的辐合运动。伴随这种高层辐散，底层辐合的运动，一支明显的次级环流出现在河南河北一带。暴雨区落在次级环流的上升支一侧，上升气流由于高空急流和低空低涡的相互作用异常增强。这种二者之间的相互作用而产生的垂直运动对暴雨的发生发展起到了重要的动力强迫作用。降水强度则随着高空急流和低空低涡的发展增强而增强。暴雨发生时，豫北地区上空存在对流不稳定的层结结构，来自孟加拉湾、南海和东海的水汽在此处聚集，这些都为暴雨的发生提供了有利的条件。

Abstract: Based on hourly merged precipitation grid dataset from the national automatic weather stations and CMORPH (Climate Precipitation Center Morphing) product and NCEP Final Operational Global Analysis (NCEP-FNL), the primary synoptic conditions and dynamic genesis of heavy rainfall happening in northern Henan and south of Hebei province during 18-21 July 2016 was analyzed with weather dynamic diagnosis methods. The results showed that heavy rainfall occurred under the favorable weather patterns of high pressure to the east and low pressure to the east. Upper-level jet stream strengthened at 200 hPa, in right side entrance region of which stronger divergence appeared. Southwest vortex at 700 hPa strengthened and moved eastward in the lower level, leading to the convergent motion in its northeast side. Along with the divergence in higher level and con-vergence in lower level, an obvious secondary circulation occurred over Henan and Hebei province. Rainstorm area was under the ascending motion side, which was abnormally enhanced because of the interaction between the upper level jet stream and low level vortex. The vertical motion caused by the interaction between them had an important dynamic force effect on the generation and development of the heavy rainfall. Precipitation intensity was enhanced, following the development of the upper-level jet stream and low level vortex. Atmospheric structure of convective instability existed over the northern area of Henan province when the heavy rainfall happened. And moisture coming from Bay of Bengal, South China Sea and East China Sea gathered here. All of these were favorable for the generation of the heavy rainfall.